Merge changes Ia5df853c,Idf15ff5d,I383f1bb9,I0d6a8e4f into tm-qpr-dev

* changes:
  Switching UserSwitcherController implementation.
  Feature flag for UserSwitcherController refactor.
  Extracts interface from UserSwitcherController.
  Cleans up UserSwitcherController API.